This invention relates in general to vehicular drive train balancing systems and in particular to an apparatus for dynamically balancing a combined assembly of a drive shaft and axle input shaft for such a vehicle drive train system.
Most vehicles provide a drive train system for transmitting power from a source of rotational power, such as an internal combustion or diesel engine, to a plurality of rotatably driven wheels. A typical drive train system includes a clutch, a transmission, a drive shaft, and an axle connected between the engine and the driven wheels. The clutch is connected to the engine for selectively providing a driving connection therethrough to the transmission. The transmission provides a plurality of speed change gear ratios between the clutch and the drive shaft. The drive shaft is elongated so as to transmit the rotational power from the transmission to the vicinity of the driven wheels. The axle includes an elongated input shaft which is connected to the drive shaft, a differential which is rotatably driven by the input shaft, and a pair of output axle shafts which connect the differential to the driven wheels. All of the connections between the components of the drive train are typically accomplished by universal joints or similar couplings which permit the two components to be oriented at varying angles relative to one another during use.
A typical drive shaft may be formed from an elongated cylindrical tube having a pair of universal joints secured to the ends thereof. Alternatively, a drive shaft may be formed from two (or more) elongated cylindrical tubes which are connected together by universal joints, and which further including a pair of universal joints secured to the ends thereof. As used herein, the term "drive shaft" includes the overall assembly of both the tube (or tubes) and the universal joints secured thereto. Because of manufacturing inaccuracies, both the tubes and the universal joints are typically unbalanced for rotation. Thus, when the tubes and the universal joints are assembled, the drive shaft is generally also unbalanced for rotation. Similarly, the input shafts of the axles are also typically unbalanced for rotation during use.
It is well known that undesirable noises and vibrations are generated during use if the drive shaft and the axle input shaft are not precisely balanced for rotation. Thus, it is known to balance the drive shaft and the axle input shaft individually before installation into the vehicle drive train system. Many fixtures are known in the art for individually balancing these components. However, it has been found that when an individually balanced drive shaft and an individually balanced axle input shaft are connected together in the vehicle drive train system, the combined unit may be unbalanced for rotation. This occurs even though the drive shaft and the axle input shaft may have been carefully balanced individually before installation. The unbalance of the combined unit results from the summation of the smaller individual unbalances of the drive shaft and the axle input shaft when connected together.
In the past, it has been attempted to address this combined unit unbalance by connecting together slightly unbalanced drive shafts and axle input shafts, such that the individual unbalances reduce the overall unbalance of the assembly. While this method is somewhat effective, it is difficult and time consuming. Accordingly, it would be desirable to provide an apparatus for dynamically balancing the combined assembly of a drive shaft and an axle input shaft before installation in the vehicle drive train system.